碳纳米管含量对TiAl基合金微观组织及室温力学性能的影响

Effect of carbon nanotube content on microstructure and room temperature mechanical properties of TiAl-based alloy

首先采用超声波震荡和机械球磨的方法将碳纳米管(CNTs)粉末和Ti-48Al-2Cr-8Nb(原子分数,%)预合金粉末制备成混合粉末,随后通过放电等离子烧结技术(SPS)制备了CNTs/Ti-48Al-2Cr-8Nb复合材料,研究了CNTs含量对复合材料的相组成、微观组织和室温力学性能的影响。结果表明:随着CNTs含量的增加,反应生成的TiC和Ti_(2)AlC碳化物的含量会增加,而TiC、Ti_(2)AlC相可以细化晶粒尺寸,起到细晶强化作用,同时TiC、Ti_(2)AlC相作为硬质陶瓷相也可以起到强化作用;当CNTs含量为0.4%时,复合材料的平均晶粒尺寸由60μm细化到32μm,密度、硬度和抗弯强度分别为4.294 g/cm^(3)、377 HV20和879 MPa,断裂模式主要为穿晶断裂;当CNTs含量较多时,由于CNTs分散不均匀,反应生成的碳化物会发生团聚现象,造成复合材料会产生凹坑、裂纹等缺陷,降低其室温力学性能。

Firstly,carbon nanotubes(CNTs)powders and Ti-48Al-2Cr-8Nb(at%)pre-alloyed powders were prepared into mixed powders by ultrasonic vibration and mechanical ball milling,and then CNTs/Ti-48Al-2Cr-8Nb composites were prepared by spark plasma sintering(SPS).The effect of CNTs content on phase composition,microstructure and room temperature mechanical properties of the composites was studied.The results show that with the increase of CNTs content,the content of TiC and Ti_(2)AlC carbides will increase,and TiC and Ti_(2)AlC phases can refine the grain size to induce fine grain strengthening,and also as hard ceramic phases they can also act as the strengthening component.When the CNTs content is 0.4%,the average grain size of the composites decreases from 60μm to 32μm,the density,hardness and bending strength are 4.294 g/cm^(3),377 HV20 and 879 MPa,respectively,and the fracture mode is mainly transgranular fracture.When the content of CNTs is high,due to the uneven dispersion of CNTs,the carbides produced by the reaction will agglomerate,resulting in the defects such as pits and cracks,which will reduce the room temperature mechanical properties of the composites.